Circuit arrangement with means for obtaining safety standards



y 1963 A. R. CORNELL 3,089,982

cmcuxw ARRANGEMENT WITH MEANS FOR OBTAINING SAFETY STANDARDS Filed July 18, 1960 F i 9- 3 INVENTOR Archie "R. Corngll wnNEssQEs? q/ A I I BY ATTORNEY United States Patent Ofitice 3,689,982 Patented May 14, 1963 3,089,982 CIRCUIT ARRANGEMENT WITH MEANS FOR OBTAlNlNG SAFETY STANDARDS Archie R. (Iornell, Avon Lake, ()hio, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed July 18, 1960, Ser. No. 43,514 6 Claims. (Cl. 315-98) The present invention relates to circuit arrangements for supplying energy to electrical load apparatus, and, more particularly, to means for obtaining, in such arrangements, characteristics which conform to prescribed safety standards.

The employment of a circuit arrangement for any designated purpose carries along with it a need for limiting current and potential associated with any exposed portion of the arrangement, relative, for example, to ground, to values which comply with reasonable safety standards, particularly when the arrangement is to be handled by field installers and service men or other individuals who have reason to handle the arrangement. For standardizing purposes, independent associations establish the safe current and potential values for what are considered to be xposed circuit portions of standard or other apparatus.

Recognizably, the mere obtaining of safety currents and voltages might not be a unique matter of itself, but to provide novel means for obtaining safety objectives with considerable economy is a noteworthy advance particularly when conventional means are not provided with such economic character. To exemplify the point being made, one might consider a circuit arrangement which is formed for supplying power, on the order of 4d watts, for example, to electrical load apparatus, such as fluorescent lamps or other discharge devices.

Such an arrangement usually includes a device or a number of devices or lampholders for engaging or holding the exemplified lamps. Shock hazard during insertion of the lamps in the holders has been determined to be reduced reasonably if the current which flows through a 500 ohm resistor in a path from the free terminals of either of the lampholders to ground is limited to 5 milliamperes or if the voltage to ground across the noted path from the terminals of either of the lampholders is limited to 180 volts. Alternatively, the lampholders can be manufactured to have inaccessible live parts or to provide inherent circuit interruption unless the lamp, or lamps, are assembled therewith. However, contrary to provisions of the present invention, each of the latter or alternate schemes for avoiding shock hazard is prohibitively expensive and therefore commercially undesirable.

It is to be noted that once the lamp or lamps are positioned in the holders to be connected with the circuit arrangement, the indicated safety values of current and voltage are no longer as critical, for then the possibility of forming a path through a grounded individual from the lampholder terminals is virtually precluded in that the lampholder terminals are not then conductively exposed, either directly or indirectly, through the lamp and its terminals, such as the terminal pins conventionally provided with what is known as the Rapid-Start type of fluorescent lamp.

Clearly, a skilled artisan can add circuit components to the circuit arrangement now being considered in order to limit the current and voltage as prescribed. For example, a resistor which is connected serially in a ground circuit loop including the output of the circuit arrang ment could be provided with suflicient resistance to enable the safety values of current and voltage to be obtained. However, such an obtained result is clearly accompanied by the added expense of the additional circuit component and, perhaps, more importantly, by the added expense which arises in forming and operating the circuit arrangement. The present invention avoids the foregoing defects, as to the matter of economy, in conventional arrangements by providing safety means which are formed principally by the inherently necessary operational components themselves without adding separate components, without complicating the necessary components, and without enlarging power losses.

The preceding general remarks have been set forth only to provide a fuller perspective of the invention, particularly in conjunction with the more specific and ensuing descriptive matter.

Thus, it is an object of the invention to provide a novel circuit arrangement having means for obtaining safely valued electrical characteristics with economy.

It is an additional object of the invention to provide a circuit arrangement of the character just described through a unique interrelation of the operationally necessary components of the arrangement.

It is a further object of the invention to provide a circuit arrangement of the character thus far described in which the operationally necessary circuit components are arranged to enable an overall reduction of real power loss and therefore to enable components which are of relatively smaller size to be used.

Another object of the invention is to provide a novel circuit arrangement which is automatically deenergized when its load apparatus is removed therefrom.

An additional object of the invention is to provide a novel circuit arrangement having means for heating filaments of its load apparatus, with at least a portion of the heating means being formed by operationally necessary components of the arrangement rather than separate inductive windings.

These and other objects of the invention will become more apparent upon consideration of the following detailed description of an illustrative embodiment of the invention as related .to the attached drawing, in which:

FIGURE 1 is a schematic view of a circuit arrangement formed in accordance with the principles of the invention for starting and operating discharge devices;

FIG. 2 is a top plan view of an exemplary'construction of inductive means shown as a part of the circuit arrangement in FIG. 1;

FIG. 3 is a schematic view of an alternate circuit arrangement embodied in accordance with the precepts of the invention; and

FIG. 4 is a top plan view of an exemplary construction of inductive means shown as a part of the circuit arrangement in FIG. 3.

With regard to the broad precepts of the invention, a circuit arrangement includes a group of circuit components which are interconnected in a manner such that operationally necessary functions of the arrangement are performed and such that means are formed for limiting or precluding the appearance of unsafe current or voltages at exposed portions of the arrangement, such as the out-put terminals. In addition, the manner of interconnection of the circuit components enables at least a portion of one of the components to be energized by means including another conventionally necessary component such that the need for still another conventional component is eliminated. To illustrate more clearly but not to limit these broad principles of the invention, the detailed description will now be set forth.

With reference to FIGS. 1 and 2, a circuit arrangement 10 is provided for energizing load apparatus, here in the form of a discharge device or fluorescent lamp 12. A voltage source 14, such as an alternating one, is employed for energizing the circuit arrangement 10 through input terminals 16 and 18. Since the lamp .12 is typical of load apparatus for which elevated values of voltage are necessary for starting or operation, inductive means 20, of the exemplified construction shown in FIG. 2, are employed for supplying operationally required voltages and currents.

Characteristically, the fluorescent lamp 12, which can be one of the aforementioned Rapid-Start type, is provided with heater or filament elements 22 and 24 for establishing and maintaining an electrical discharge along a substantially longitudinal path through the lamp 12. To provide for conducting energy to the filament elements 22 and 24, pin-like terminals 25, 26 and 27, 28 are provided, respectively.

The inductive means 29 include a primary winding 30 which can be energized by the voltage source 1.4. Inductively coupled with the primary Winding 39, is a secondary winding 32 for providing, in conjunction with the primary winding 30, an elevated voltage across the lamp 12 between the filament elements 22 and 24, particularly under starting conditions. The inductive means include a core 33, suitably formed, as with laminations if desired, of magnetic material, such as silicon steel, to enable the inductive coupling between the primary winding and the secondary winding 32 to be accomplished efiiciently. In addition, as viewed in FIG. 2, a shunt path 35 having a gap 37 can be included in the core 32 so that the secondary winding 32 is characterized with relatively high reactance for ballasting purposes. A portion 36 of the secondary winding 32 is also desirably employed to supply energy for heating the filament 22.

The secondary winding 32 and the primary winding 30 are connected in the form of a serial branch of the circuit arrangement 16 in order to provide additively a starting voltage across the lamp filaments or electrodes 22 and 24. Once a discharge has been initiated through the lamp 12, the voltage required for sustaining the discharge is considerably reduced and can be effected substantially by that of the source 14 diminished by the reactance drop across the secondary winding 32. Of course, the discharge through the lamp 12 and therefore through the secondary winding 32, having a resulting tendency to increase in value, is limited by the impedance effect of the high reactance of the secondary winding 32.

In order to offset the fact that the serial combination of the lamp 12 and the high reactance secondary winding 32 would ordinarily cause the supply current to lag the supply voltage, means are included for providing a leading current through a branch of the circuit arrangement 10 which is in parallel with the primary winding 30 and, perhaps more pertintently, in parallel with the serial combination of the lamp 12 and the secondary winding 32. This means include in this example a serial combination of another winding 38, of the inductive means 20, being inductively coupled with the primary winding 39, and a capacitor 40. Of course, other serial combinations could be used so long as the proper phase impedance were provided to enable the compensatory leading current to exhibit the proper phase and magnitude.

It is particularly to be noted that the heater or filament 24, being serially connected with the parallel combination of the primary winding 30 and the impedance means 38 and 40, is energized by the current through the primary winding 3% and by the compensatory current through the impedance means 38 and 40, with the latter currents being summed vectorially at any instant of time. In view of the foregoing analysis, it is clear that operational or load current flows from the voltage source 14 through the terminal 16, to the secondary winding 32, through the lamp 12 to return, finally, through conductor 41 to the terminal 18 and the voltage source 14. As such, the current which flows through the primary winding 30 during normal operation is principally the magnetizing current, which is necessary to maintain the core 33 in a magnetized state, and the net current induced therein as a reflection of the currents flowing in the windings 32 and 38.

The design parameters of the primary winding 30 and the impedance means 33 and 49 can be adjusted to provide a value for the continuous current through the heater element 24 so as to create, consistently with previous considerations, the desired amount of heating. Through the utilization of currents which are otherwise operationally necessary, the circuit arrangement 16 therefore eliminates the need for providing a separate wind ing, similar to the winding 36, for energizing the heater element 24.

At the outset of this description, it was noted that prescribed safety objectives can also be attained with the use of the invention. The means for obtaining these safety objectives comprise the described components of the circuit arrangement 10 as interconnected. Certainly, if the circuit arrangement 10, except for the lamp 12, were installed, any individual, such as a service man, who had partially installed the lamp 12 such that the pinlike lamp terminals 25 and 26 were engaged with respectively associated terminals 42 and 44 of a lampholder (not shown), could not be shocked if any part of his body were grounded and he touched either of the other lamp terminals 27 or 28 prior to their engagement, respectively, with terminals 46 and 4-8 of another lampholder (not shown).

This result follows from the fact that without the lamp terminals 27 and 28 being engaged with the lampholder terminals 46 and 43, the voltage source 14 is precluded from energizing or magnetizing the primary winding 38 because of an interruption in the energizing circuit adjacent the lampholder terminal 46. Hence, not only are currents and voltages associated with exposed circuit portions limited from exceeding upper safe values, but they are precluded from attaining substantially any value during the lamp inserting procedure. This is true even if the lamp 12 were inserted such that the terminals 27 and 28 were first engaged with the lampholder terminals 46 and 48. In the latter case, although the primary winding 30 woud become energized, a grounded individual would experience no shock upon touching the exposed terminals 25 and 26 of the lamp 12 since the engaged terminals 27 and 28 are also substantially at ground potential and since ordinarily one of the source leads or conductors, such as the conductor 18, is grounded. However, if the conductor 18 is not grounded, a ground connection can be made thereto, if desired, through a resistor 50 to ensure that the lamp terminals 27 and 28 are maintained substantially at the ground potential as just described.

Of perhaps greater significance in the matter of the ground connection just noted, is the fact that the resistor 50, if connected to or grounded through a fixture (not shown) for the lamp 12, can retain the terminal 51 and the filament 24 substantially at the potential of the fixture. If the resistor 50 is provided with substantial resistance, such as a value of 1 megohm, the fixture is, for all practical purposes, precluded from forming a path for any current, yet is sustained substantially at and in fixed relation to the potential of the filament 24 to enable the potential gradient, which is auxiliarly employed for starting, from the filament 22 to the fixture always to be in reference to the fixed potential value of the filament 24.

Similar results are obtained through the use of an alternate arrangement 68 depicted in FIGS. 3 and 4. In the alternate arrangement 60, elements which are similar to elements described in connection with FIGS. 1 and 2 have been accorded corresponding reference characters. Thus, in the alternate arrangement 60, the secondary winding 38 included in the arrangement 10 is removed, and a capacitor 62 is interposed serially in the circuit branch including the high reactance secondary winding 32 and the lamp 12 to provide a ballasting effect resulting in a leading load current. If desired, the heater winding 36 can be separately wound on the provided core 31.

To correct the circuit power factor and to contribute to the determination of the reactance of the secondary winding 32, a bridged gap 64 is included in the core 31. By suitably sizing the gap as, the primary magnetizing current, which is a lagging one, can be established so as substantially to unify the power factor and so as to determine the amount of primary flux which can be linked with the secondary winding 32. It is to be noticed that in the arrangement 60, as described in connection with the arrangement 10, the filament 24 is energized through the use of the primary current, including the magnetizing component, and forms an interruptable link in the circuit loop including the source 14 and the primary winding 30 to provide the safety features already related.

In the foregoing description, the respective modes of operation of several embodied arrangements of specific circuit elements have been related only to point out the principles of the invention. The description, therefore, has only been illustrative of the invention, and, accordingly, it is desired that the invention be not limited by the embodiments described here, but, rather, that it be accorded an interpretation consistent with the scope and spirit of its broad principles.

What is claimed is:

l. A circuit arrangement for energizing a discharge device having heater elements or the like as described, said arrangement comprising inductive means for transforming the voltage of a source to enable said device to be started and for ballasting said device during its operation, means including a capacitor being connected across a primary portion of said inductive means for correcting the power factor of the circuit arrangement, and means for energizing said heater elements, said energizing means effecting the energization of at least one of said heater elements by enabling the primary current of said inductive means and the current through said capacitor to be directed therethrough.

2. A circuit arrangement for energizing a discharge device having heater elements or the like as described, said arrangement comprising inductive means for transforming the voltage of a source, said inductive means including a primary portion and a high reactance secondary portion which are serially correlated for the purpose of starting said device, said high reactance secondary portion providing a ballasting effect for said device, said inductive means also including another secondary portion being serially connected with capacitance means to be substantially across said source for correcting the circuit power factor, and means for energizing said heater elements, said energizing means including said primary portion of said inductive means serially connected with at least one of said heater elements to enable at least the primary current of said inductive means to be directed therethrough.

3. A circuit arrangement for energizing a discharge device having heater elements or the like as described, said arrangement comprising inductive means for transforming the voltage of a source, said inductive means including a primary portion and a high reactance secondary portion which are serially correlated for the purpose of starting said device, said secondary portion providing a ballasting effect for said device during its operation, and means for energizing said heater elements, said energizing means including said primary portion of said inductive means serially connected with said source and with a pair of spaced terminals across which at least one of said heater eleme t is o e ne te to pro ide h t prio to ins allation of said device across said terminals the arrangement is precluded from being energized.

4. A circuit arrangement for energizing a discharge device having heater elements or the like as described, said arrangement comprising inductive means for transforming the voltage of a source, said inductive means including a primary portion and a high reactance secondary portion which are serially correlated for the purpose of starting said device, said high reactance secondary portion and capacitance means being included serially in a circuit branch including said device to produce a leading ballasting elfect for said device, a bridged gap being included in a magnetizable core of said inductive means to control the magnetizing current through said primary portion and thereby to provide for substantially unifying the circuit power factor, and means for energizing said heater elements, said energizing means including said primary portion of said inductive means serially connected with at least one of said heater elements to enable at least the primary current of said inductive means to be directed therethrough.

5. A circuit arrangement for energizing a discharge device having heater elements or the like as described, said arrangement comprising inductive means for transforming the voltage of a source, said inductive means including a primary portion and a high reactance secondary portion which are serially correlated for the purpose of starting said device, said high reactance secondary portion providing a ballasting effect for said device, said inductive means also including another secondary portion being serially connected with capacitance means to be substantially across said source for correcting the circuit power factor, and means for energizing said heater elements, said energizing means including said primary portion of said inductive means serially connected with at least one of said heater elements to enable at least the primary current of said inductive means to be directed therethrough, said one heater element being grounded upon connection through resistive means so that even if during installation of said device said one heater element is first connected to energize said arrangement the hazard of shock or fire is substantially eliminated.

6. A circuit arrangement for energizing a discharge device having heater elements or the like as described, said arrangement comprising inductive means for transforming the voltage of a source, said inductive means including a primary portion and a high reactance secondary portion which are serially correlated for the purpose of starting said device, said high reactance secondary portion providing a ballasting effect for said device, said inductive means also including another secondary portion being serially connected with capacitance means across said primary portion for correcting the circuit power factor, and means for energizing said heater elements, said energizing means including said primary portion of said inductive means in a combination with said secondary portion and said capacitance means, said combination being serially connected to at least one of said heater elements to enable the primary current and the power corrective current to be directed therethrough.

References Cited in the file of this patent UNITED STATES PATENTS 2,940,008 Strecker June 7, 1960 FOREIGN PATENTS 494,585 Belgium July 17, 1950 ,4 Gr at rita n. --r-v--- --r--. Oct- 3, 1956 

1. A CIRCUIT ARRANGEMENT FOR ENERGIZING A DISCHARGE DEVICE HAVING HEATER ELEMENTS OR THE LIKE AS DESCRIBED, SAID ARRANGEMENT COMPRISING INDUCTIVE MEANS FOR TRANSFORMING THE VOLTAGE OF A SOURCE TO ENABLE SAID DEVICE TO BE STARTED AND FOR BALLASTING SAID DEVICE DURING ITS OPERATION, MEANS INCLUDING A CAPACITOR BEING CONNECTED ACROSS A PRIMARY PORTION OF SAID INDUCTIVE MEANS FOR CORRECTING THE POWER FACTOR OF THE CIRCUIT ARRANGEMENT, AND 